The Enttec DMX unit is a good option, although you will need the following external to use it with Max.

http://www.nullmedium.de/dev/dmxusbpro/

A dimmer-pack allows you to vary the voltage of an electrical supply to dim a lighting fixture. Be warned however that you can't plug just anything into a dimmer. Anything with complex electronics, or indeed anything more complicated than a simple bulb is it risk of being damaged if supplied by a dimmer. This is because dimmers do not produce a smooth sine wave of AC voltage, there are numerous spikes and harmonics in the supply.

On the software side of things, take a look at the following link. The manual also has a lot of advice for using DMX rigs.

http://www.theimpersonalstereo.com/software/imp-dmx/

What exactly are you turning on/ off? If it's just DC powered stuff you could do it very cheaply with an Arduino (without having to code using Maxuino) and a very simple circuit that uses a transistor as a switch. I'm sure theres something you could do with AC stuff but I wouldn't mess with it!

Attached circuit, just replace solenoid with your DC item, power with your required power source and PIC output would be a pin from the Arduino.

Actually, I'm needing to turn fluro lighting tubes on and off, its for a performance based piece.

I saw 'dimmer' on this model and assumed I could use it to send on/off signals to electrical appliances (like lights or stereo's, for example), OR then if I had lights only, I could use a dimmer switch.

Is this right? Like I said, still learning :)

I have never played with anything arduino related, so its like looking down another wormhole at the moment. I would like to stay based in the max/msp world if possible, as my projects tend to build on each other over time. But the idea of a 'maxuino' sounds a little more tempting. But I'm still not sure of the advantages of doing so. Is it just the fact that you can run it off relatively cheap hardware as opposed to a computer set up?

Sounds like you want to go with a DMX dimmer/relay pack. For tubes you want to use the relay switching mode, NOT the dimmer mode (as far as I know). The Chauvet pack you linked enables you to set some channels to relay mode and some to dimmer mode which is nice and adaptable, whereas the Elation one looks like you can only set the whole pack as dimmer or relay mode.

Arduino combined with Max and Maxuino enables you to do a lot of hardware interfacing without having to get out of your Max comfort zone, but in this case you'd either be playing with high voltage AC which is dangerous and not recommended, or I suppose you may be able to find an off the shelf inverter to convert a low voltage DC power source into AC which could be tacked on to the circuit I attached. I don't know enough about that to advise you really.

I've just stumbled across this thread and David's comment has me wondering: Would a dimmer pack (dmx controlled) work OK with simple motors? I want to control the voltage (motor speed) variably via sliders. I know that most would go Arduino to powerswitch tail, but for another project I'm considering the Enttec USB Pro Mk2, which has a Standalone mode. In my possibly/likely faulty thinking, I could run motors (as part of a kinetic installation) from the Mk2 without the computer. The standalone mode records changes in values as well as durations.

I wouldn't recommend it. Standard dimmer electrical output waveforms don't look anything like standard AC because they work by cutting off the supply at a certain point in the leading (or trailing) edge of each sine wave. This means they will mess up most electronics and motors that depend upon receiving a clear sine wave. You might be able to get away with it (I know a lot of theatres park their dimmers at 100 % to power things that need a constant supply like moving lights), but it's bad practice and you risk severely damaging anything you plug into it.

I suggest you build a DMX (or Art-Net) controlled Arduino motor board, then you can run the a show from the Enttec box in standalone mode. As a side-note, you shouldn't be using DMX to control anything where safety could be an issue (pyro or movement of large objects), but small motors are fine.

Thanks David- this helps me tons. I hadn't considered a DMX shield for Arduino for that specific purpose. Excellent. I'll look into Art-Net too; my fixation on the standalone mode might not be the crux of these projects.